The disease typically affects women in their fourth or fifth decade of life with a mal-e:female ratio of 1:2-3. Children and adolescents are rarely involved. In 40-60% of cases, the joint disease precedes skin and mucosal involvement. Patients tend to present with polyarthritis, which most commonly affects the distal interphalangeal joints of the hands. Other joints may also be involved. Whatever the anatomic location, the arthritis in MR is symmetrical, chronic, and destructive. Radiological examination shows well-circumscribed periarticular "punched out'' erosions and reabsorption of the juxtarticular zone corresponding to a secondary osteo-arthritis (1).
The skin lesions in most cases are firm, reddish, brown or yellow papules, nodules, or plaques ranging in diameter from a few millimeters to centimeters located in a somewhat symmetrical fashion predominantly on the extensor surfaces of the hands and forearms (Fig. 1). The face, scalp, and hands are also commonly involved. Multiple confluent lesions of the face may result in leonine facies. Very typical if not pathognomonic are the rings of papules along the nail folds (coral
Figure 1 Multicentric reticulohistiocytosis: multiple papules and nodules in typical acral locations.
bead-like lesions) seen in a third of patients. They sometimes produce nail dystrophy. Although observed less frequently, vermicular erythematous lesions bordering the nostrils are also quite characteristic of MR (2). Involvement of the lower trunk and the legs is rarely seen. The skin lesions, which rarely ulcerate, are often in proximity to the affected joints. Pruritus is reported in about 25% of cases.
About half of the patients have mucosal involvement affecting the oral mucosa, lips, tongue, nasal mucosa, pharynx, larynx, and sclera (3). Cystic swellings of tendon sheaths may also develop. Constitutional symptoms include fever, malaise, and weight loss. Lymphadenopathy is present in 3% of cases (2). Laboratory findings are usually normal.
An associated internal malignancy including carcinomas of internal organs, multiple myeloma, melanoma, and lymphomas is found in about 15-25% of patients (4-6). In most cases, the diagnosis of MR precedes that of the neoplasm. In approximately 15% of cases, MR is accompanied by an autoimmune disease such as Sjogren syndrome or systemic lupus erythematosus (7,8).
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